Posts Tagged ‘EBS’

We have all been dealing with on-premises infrastructure for years before public cloud became a thing. Depending on complexity and size of your environment, retention and other requirements you can choose from plethora of products, such as Veeam, Commvault, NetWorker, you name it.

When public cloud started getting more traction we realised that the paradigm has shifted. Public cloud providers are pushing us to treat instances of application servers as cattle versus pets and build fault tolerance into code and not rely on underlying infrastructure reliability.

If application is no longer monolithic and is distributed among multiple instances of the same server, loss of any one instance has little overall impact on the application and does not require a restore. We can simply spin up a new instance instead.

However, majority of applications in today’s IT environments are still monolithic and need to be backed up. Data needs to be protected as well, if it gets corrupted or if for any other reason we need to roll back our application to a certain point in time, backups are necessary.

AWS Snapshots

When I started researching the topic of backup in the cloud I realised that it is still a wild west. Speaking of AWS specifically, if you are using one of the native AWS services, such as RDS, you would usually have the backup feature built-in. Otherwise, if you simply want to backup some application or service running inside an AWS instance, all you have is snapshots.

We have all heard the mantra, that snapshot is not a backup, because usually it is kept in the same place as the original data it was created from. This is true for most of the traditional storage arrays. AWS is slightly different.

Typically when you start an EC2 instance, its disk volumes are kept on Elastic Block Store (EBS), which is an equivalent of block storage in traditional infrastructure world. But when you create a snapshot of an EBS volume, the snapshot is transferred to S3 object storage.

When the first snapshot is created, the whole volume needs to be copied to S3. It may take some time to complete, depending on the volume size, but the copy process happens in the background and doesn’t impact the original EC2 instance. All subsequent snapshots will be significantly quicker, unless you overwrite large amount of data between snapshots.

CloudWatch Event Rules

As we can see, unlike traditional storage arrays, AWS snapshots are kept separately from the original data. They can even be restored to another availability zone or copied to another region to protect from region-wide failures, which makes AWS snapshots a decent backup solution. But devil is in the details.

Creating a volume snapshot manually is simple, you pick “Create Snapshot” from the Actions menu and the rest is handled by AWS. To automate the process, AWS offers CloudWatch event rules for scheduled snapshot creation. By going to CloudWatch > Events > Create Rule, setting up a schedule, selecting “EC2 CreateSnapshot API call” and the volume ID in the Target section you can implement a simple backup in AWS.

However, there are two immediate problems with such approach. The first is scalability of it. Snapshots in AWS are created on volumes, not instances. This has interesting implications, such as it is not possible to create a consistent snapshot across multiple volumes. But more importantly, if you have more than one volume on every instance, you may end up having dozens of CloudWatch rules, that are hard to manage and keep track of.

Second is retention. CloudWatch events let you create snapshots, but you cannot specify how long you want to keep them for. You will need to write your own scripts using AWS APIs to delete snapshots, which makes the whole solution questionable, as you can then use APIs to create snapshots as well.

Conclusion

As you can see, AWS does not offer a simple out of the box solution for EC2 backup. You either need to write your own scripts using AWS APIs or lean on backup solutions built specifically to solve the problem of backups in AWS. One of such solutions Cloud Protection Manager we will discuss in the next blog post of the series.